Adriana Pálffy

Isomer triggering via nuclear excitation by electron capture

Triggering of long-lived nuclear isomeric states via coupling to the atomic shells in the process of nuclear excitation by electron capture (NEEC) is studied. NEEC occurring in highly charged ions can excite the isomeric state to a triggering level that subsequently decays to the ground state. We present total cross sections for NEEC isomer triggering considering experimentally confirmed low-lying triggering levels and reaction rates based on realistic experimental parameters in ion storage rings. A comparison with other isomer triggering mechanisms shows that, among these, NEEC is the most efficient.

X-ray quantum optics

Quantum optics with X-rays has long been a somewhat exotic activity, but it is now rapidly becoming relevant as precision x-ray optics and novel X-ray light sources, and high-intensity lasers are becoming available. This article gives an overview of the current state of the field and an outlook to future prospects.

Coherence-enhanced optical determination of the 229Th isomeric transition.

The impact of coherent light propagation on the excitation and fluorescence of thorium nuclei in a crystal lattice environment is investigated theoretically. We find that in the forward direction, the fluorescence signal exhibits characteristic intensity modulations dominated by a sped-up initial decay signal that is orders of magnitude faster. This feature can be exploited for the optical determination of the isomeric transition energy. In order to obtain a unmistakable signature of the isomeric nuclear fluorescence, we put forward a novel scheme for the direct measurement of the transition energy via electromagnetically modified nuclear forward scattering involving two fields that couple to three nuclear states.

Coherent Storage and Phase Modulation of Single Hard-X-Ray Photons Using Nuclear Excitons

The coherent storage and phase modulation of x-ray single-photon wave packets in the resonant scattering of light off nuclei is theoretically investigated. We show that by switching off and on again the magnetic field in the nuclear sample, phase-sensitive storage of photons in the keV regime can be achieved. Corresponding π phase modulation of the stored photon can be accomplished if the retrieving magnetic field is rotated by 180°. The development of such x-ray single-photon control techniques is a first step towards forwarding quantum optics and quantum information to shorter wavelengths and more compact photonic devices.

Dominant Secondary Nuclear Photoexcitation with the X-ray Free Electron Laser

The new regime of resonant nuclear photoexcitation rendered possible by x-ray free-electron laser beams interacting with solid state targets is investigated theoretically. Our results unexpectedly show that secondary processes coupling nuclei to the atomic shell in the created cold high-density plasma can dominate direct photoexcitation. As an example, we discuss the case of

Nuclear excitation by electron capture followed by fast x-ray emission

^{93m}\mathrm{Mo}

Electric-dipole-forbidden nuclear transitions driven by super-intense laser fields

isomer depletion for which nuclear excitation by electron capture as a secondary process is shown to be orders of magnitude more efficient than the direct laser-nucleus interaction. General arguments revisiting the role of the x-ray free-electron laser in nuclear experiments involving solid-state targets are further deduced.

Nuclear effects in atomic transitions

Abstract The resonance strength of the two-step process of nuclear excitation by electron capture followed by γ decay of the nucleus can be significantly increased in highly charged ions if the resonant capture proceeds via an excited electronic state with subsequent fast x-ray emission. For fully ionized 238 92 U and 232 90 Th, the x-ray decay stabilizes the system against internal conversion of the captured electron, with an increase of both nuclear lifetimes and resonance strengths of up to two orders of magnitude compared with the case when occupied atomic orbitals prevent the x-ray de-excitation. Applications of this effect to the measurement of the not yet experimentally observed nuclear excitation by electron capture and to dense astrophysical plasmas are discussed.

Single-Photon Entanglement in the keV Regime via Coherent Control of Nuclear Forward Scattering

Electric-dipole-forbidden transitions of nuclei interacting with super-intense laser fields are investigated by considering stable isotopes with suitable low-lying first excited states. Different classes of transitions are identified, and all magnetic sublevels corresponding to the near-resonantly driven nuclear transition are included in the description of the nuclear quantum system. We find that large transition matrix elements and convenient resonance energies qualify nuclear M1 transitions as good candidates for the coherent driving of nuclei. We discuss the implications of resonant interaction of intense laser fields with nuclei beyond the dipole approximation for the controlled preparation of excited nuclear states and important aspects of possible experiments aimed at observing these effects.

Nuclear Coherent Population Transfer with X-Ray Laser Pulses

Atomic electrons are sensitive to the properties of the nucleus they are bound to, such as nuclear mass, charge distribution, spin, magnetisation distribution, or even excited level scheme. These nuclear parameters are reflected in the atomic transition energies. A very precise determination of atomic spectra may thus reveal information about the nucleus, otherwise hardly accessible via nuclear physics experiments. This work reviews theoretical and experimental aspects of the nuclear effects that can be identified in atomic structure data. An introduction to the theory of isotope shifts and hyperfine splitting of atomic spectra is given, together with an overview of the typical experimental techniques used in high-precision atomic spectroscopy. More exotic effects at the borderline between atomic and nuclear physics, such as parity violation in atomic transitions due to the weak interaction, or nuclear polarisation and nuclear excitation by electron capture, are also addressed.